[FFmpeg-user] Grabbing quality from TV card

Mike Scheutzow mike.scheutzow at alcatel-lucent.com
Wed Mar 14 16:45:26 CET 2012

Rodney Baker wrote:
> On Wed, 14 Mar 2012 06:25:12 tovis wrote:
>> Quality is still wrong, does not change against the very old Debianized
>> version. On time I have a lot of error messages:
>> $ ffmpeg -v verbose -f video4linux2 -i /dev/video0 -s 640x480 -r 25
>> out10.avi 2>&1 | tee ffmpeg-grab.log
> ...
>> [video4linux2,v4l2 @ 0x30f13e0] Setting frame size to 320x240
> ...the input is recognised as 320x240. Is this correct? If so, you're scaling 
> up the input which means you're interpolating a lot of pixels which will, in 
> turn, reduce the quality considerably.

 > Stream #0:0: Video: mpeg4 (FMP4 / 0x34504D46), yuv420p, 640x480,
 > q=2-31, 200 kb/s, 25 tbn, 25 tbc

"200 kb/s"  -> this is your output bitrate.

You are still not specifying a quality level or bitrate, so you're 
getting the default value of 200 kbits per second.

Most 640x480 material is going to look poor at this bitrate.

Mike Scheutzow

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